Problem with LEFT JOIN

[eluser]temon[/eluser]
in Four Table
categoriesSelection
categorySelectionID - categoryUrl - articleID

and

in Second Table
Comments
commentID - Comment - commentUrl

1. I suggest you using categoryID for replace categoryUrl in categoriesSelection table,
articleID for replace commentUrl in Comments table.

2. you just select from categoriesSelection table and joint other table.

try it